Microwave hyperthermia for treatment of cancers has been investigated mostly for superficial tumors and has been found to be efficacious, especially in combination with radiation and chemotherapy. There are physical and technical constraints in attempts to heat deep seated tumors from external hyperthermia applicators. An intracavitary approach may bypass some of the physical problems and to deposit microwave power close to the target tumor. The goal of this research project is to design a number of microwave intracavitary hyperthermia probes for treatment of cancers of the esophagus, vagina, cervix, uterus, rectum, prostate and bladder. In order to produce the heating patterns at the desired locations, theoretical calculations of the specific absorption rate (SAR) patterns of various insulated antennae will be conducted to predict the required physical dimensions of the probes. After the probes are constructed, they will be tested for impedance matching and optimum operating frequencies. The SAR pattens of the probes inserted at various depths in phantom tissues and operating at various frequencies will be measured with Vitek-101 temperature probes or by thermography. As a result of this study, a set of intracavitary hyperthermia probes will be available for clinical trials.